Is weekly Grid Charging Detrimental to the battery?

[jerrydelrey]

Thanks for the information everyone. I understand the process better now.

Sorry if this subject has been covered. I should have put '...for my good condition battery' at the end of the threads title.

I have concluded that I will just discharge (the best I can) and grid charge, every time I change the oil. That's approximately once a year.

When it eventaully starts to do negative recalls, I'll discharge/recharge more often.

When it dies completely, I'll get a Maxima.

Thanks again

[Cobb]

Ironically the least you use of the IMA battery the mo your mpg are too.

[3-Wheeler]

Originally Posted by jerrydelrey

.....I have concluded that I will just discharge (the best I can) and grid charge, every time I change the oil. That's approximately once a year....

Jerry,

I should also mention that I lost about 40% of my battery capacity last summer by continuing to make maximal use of the battery to/from work.

With outside temperatures at/over 100F and in-car temperatures maybe close to 130F or so, the battery lost a lot of capacity during this time. I was trickle charging with a fan at night and using up the battery during the drive in the day.

I would advise to use the battery as little as possible on those hot days.

Having MIMA really helps, as I can drive the car with absolutely no Assist/Regen whenever it is required, such as in these hot months of the year.

Jim.

[theaveng]

Originally Posted by jerrydelrey

Thanks for the information everyone. I understand the process better now.

I often get "pinged" for saying this, but to me a battery is like an organism. If you overfeed your pet organism, it causes internal damage, and if you underfeed your organism, that too causes internal damage.

A battery doesn't like going over 80% (overfeeding) or below 20% (underfeeding) because that starts to cause internal stress on its structures. Crystalization, localized overheating, sulfation, reversed cell voltages, and so forth. Nissan has started advising its Leaf EV customers not to charge their batteries over 80%, for fear it might be shortening the lifespans. (And at 20% the car goes into "turtle" mode and advises the owner to charge immediately.)

I think the "ideal" is to keep the battery at 50%, use a range of 30-70% (like a Prius), and only go 20-80% maximum. Never completely empty or completely full.

[Cobb]

Soo, would you consider this 50% half full of half empty? And is this 50% the real SOC or the cars 50% of the 80% or so it uses?

Originally Posted by theaveng

I think the "ideal" is to keep the battery at 50%

[theaveng]

No idea. I set my laptop at 50% too, in order to extend its battery life. I don't know how the meter measures the SOC.

[Cobb]

Well, Ive turned down my phev kit from 100% to 90% 120 volts vs 117. Seems the cooling fan runs less and it gives more regen braking coming to a stop although i did loose some mpg. I think a better design would need 2 converters 1 for trickle charge the ima system or supplement the idle needs, then a second one to come on with a higher setting for assist and extended ev mode use.


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[eq1]

Originally Posted by eq1

fyi, some time ago I read a NiMH chapter in a very serious academic book about batteries. As I recall, the author non-chalantly mentioned how the occasional deep discharge to NiMH batteries was common practice to increase capacity, or revive seemingly dead batteries... My take away was simply that a deep discharge was probably important to reviving weak NiMH batteries. So, point being, grid charging has nothing to do with a deep discharge....

I picked up that book again to refresh my memory on this deep discharge point. Turns out the section was about the "memory effect" with nickel-based batteries. I kind of forgot that memory effect was an issue with these batteries, or at least some people have said it is so. Anyway, I can't understand about 98% of what's written. What I can take away from just re-skimming is this: Overcharging is the cause of the memory effect. Much as Eli pointed out, oxygen production during overcharging plays a role. I think it forms some other compound that creates a secondary "voltage plateau"; basically, you end up with less and less capacity at the higher voltage potential (something like 1.34V with respect to hydrogen), and more and more capacity 'locked' in a low voltage plateau under 0.78V.

The author's passage that I honed-in on during my first reading was this: "It is also widely known that this problem can be 'cured' by subjecting them to a slow, deep discharge." Most of the section builds a case for overcharging being the cause of the so-called memory effect, rather than repeated shallow discharges, discharges without fully draining the battery...

So, to the extent that memory effect is a problem with our batteries, grid charging would likely do nothing to help. The potential impacts of overcharging while grid charging or after grid charging and then driving shouldn't be overlooked. For instance, grid charging weekly, especially longer soak charges, should probably be avoided...

[3-Wheeler]

Originally Posted by eq1

.....What I can take away from just re-skimming is this: Overcharging is the cause of the memory effect. Much as Eli pointed out, oxygen production during overcharging plays a role. I think it forms some other compound that creates a secondary "voltage plateau"; basically, you end up with less and less capacity at the higher voltage potential (something like 1.34V with respect to hydrogen), and more and more capacity 'locked' in a low voltage plateau under 0.78V......

eq1,

Did the author mention anything about the RATE at which the battery is topped off, has an effect on this phenomena?

Or is it just the fact that the battery is over-voltaged at all, causes this?

Thanks, Jim.

[JohnVirginia]

Originally Posted by eq1

The potential impacts of overcharging while grid charging or after grid charging and then driving shouldn't be overlooked. For instance, grid charging weekly, especially longer soak charges, should probably be avoided...

WRT ..."then driving shouldn't be overlooked" aren't there enough gizmos, spoofing of signals, etc. in existence to stop all of the car's charging (normal, background, regen) until normal self discharge or assist brings the charge back down to the safe mark? If not, what is left/needed? I've read so many posts I am getting unable to sort them out.